The accumulation of various substances in tissues and organs of the body can be an indicator of certain conditions or diseases. For example, accumulation of fat-containing substances in the liver is an indicator of fatty liver disease, the most common cause of chronic liver disease in the United States. In addition, in the United States, the prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing and has been estimated to affecting up to 30% of the general population. Although NAFLD was initially thought to be a benign condition, it has been increasingly recognized as a major cause of liver-related morbidity and mortality, capable of progressing to cirrhosis, liver failure, and hepatocellular carcinoma. With the rise of obesity and diabetes in United States, the prevalence of NAFLD is expected to continually increase.
Other accumulations in the body can be a significant indicator of other conditions and diseases as well. For example, accumulations of plaque in arteries can be an indicator of heart disease. Unfortunately, conventional techniques for detecting and quantifying substances in the liver, arties, and other tissue and organs of the body have many disadvantages. Many are invasive and/or expensive. For example, a needle biopsy is invasive and poorly suited as a diagnostic test in such a prevalent condition because of its expense and risks of complications. Available non-invasive imaging techniques, such as MR imaging and CT scans, are expensive and can have other disadvantages (e.g., exposure to ionizing radiation).
Accordingly, there is a need for improved systems and methods for assessing the condition of tissues and organs, and in particular, for detecting and quantifying the accumulation of these substances therein.